The present invention relates to a key switch device and more particularly to a key switch device of a link type to be suitably used for a thin keyboard in a personal computer of a notebook type.
For example, Japanese Patent Publication No. 2001-283675A discloses a key switch device of a link type as shown in FIG. 6. In the key switch device, a rubber spring 3 is attached to a portion between a board 1 and a key top 2, and the key top 2 is formed to be movable upward and downward. Furthermore, a small link 4 and a large link 5 which are pivotable in directions orthogonal to each other are provided between the board 1 and the key top 2 so as to not come in contact. The small link 4 is formed by a synthetic resin and the large link 5 is formed by a U-shaped wire.
The small link 4 is slidably attached to a slide guide (not shown) having a lower end provided on an upper face of the board 1. Furthermore, a pivot shaft portion 7 formed at an upper end of the small link 4 is pivotably supported on a pivot support 8 formed with a slit and provided on a back face of the key top 2. In addition, an upper end and a lower end in the large link 5 are pivotably supported on pivot supports 9 and 10 formed on the upper face of the board 1 and the back face of the key top 2, respectively.
The key top 2 is held on the small link 4, the large link 5 and the rubber spring 3 so that a stable stroke in a vertical direction can be secured.
In a Z-link mechanism in the above key switch device, however, upper and lower ends of the large link 5 are pivotably coupled and held on the pivot supports 9 and 10, so that the large link 5 carries out a pivoting motion around a pivot shaft portion thereof held on the pivot support 10 of the board 1. When the key top 2 is pressed down, therefore, it is not moved vertically but is moved in a slightly horizontal direction by a dimension D. Accordingly, it is necessary to carry out a design that secures a key top space corresponding to the dimension D.
Moreover, since a clearance is made between the large link 5 and the key top 2, the clearance generates a looseness of the key top 2.